This invention generally relates to machines for forming articles from a moving web of film that carries an attached or integrally formed object (or objects). In particular, the invention relates to machines for manufacturing reclosable bags from a moving web of film that carries one or more slider-zipper assemblies.
The invention can be utilized in conjunction with many different methods of and machines for making reclosable bags. In particular, the invention has application in automated production lines that incorporate a “bag machine”, which makes reclosable bags without filling them with product, and automated production lines that incorporate any one of a variety of form-fill-seal (FFS) machines, which produce sealed reclosable bags filled with product. In particular, the invention has application in machines that form a package, fill it with product, and then seal the product inside the package using any one of the known FFS methods, such as HFFS (horizontal form-fill-seal), VFFS (vertical form-fill-seal) with the zipper applied in either the machine or transverse direction, or HFVFS (horizontal form/vertical fill-seal).
In either case (bag machines or FFS machines), the slider may need to pass between sets of rollers during the manufacturing operations. In some cases, flanged zipper strips with sliders thereon pass between rollers on their way to a zipper application station where one or both of the zipper flanges is (are) joined to a web of bag making film. Thereafter, the web of film, with attached zipper or slider-zipper assemblies, passes through other rollers on its way to or inside a bag machine or a form-fill-seal machine. In the case of flangeless zippers (also known as “string zippers”), typically the backs of a pair of interlocked flangeless zipper strips are attached to a folded web of bag making film. In a recent development, sliders are inserted on the string zipper. The string zipper-film assembly with sliders may then pass through rollers on its way toward a filling station or out of a bag machine.
Optionally, the zipper and the web of bag making film can be extruded together, in which case the web and zipper are an integral formation, rather than an assembly. However, the integral formation of the zipper and web does not preclude the insertion of sliders on the zipper, in which case, again, the entire assembly may need to pass between rollers at some stage during further manufacturing operations.
Typically, such machines that move a web of film incorporate drive or pinch rollers for tensioning and moving the film through the machine. The web may be advanced through the machine either continuously or in discrete advancements separated by dwell times (i.e., intermittently). Any attachments to the web of film necessarily move with the web and must be passed through the pinch rollers. However, sliders cannot feasibly be passed through the nip formed by two pinch rollers.
It is well known to use rollers having hard surfaces, meaning surfaces that are not resilient and that cannot conform to the shape of an attached object when a film carrying that object is passed through the nip of the rollers. It is also known to provide a peripheral annular groove in one or both rollers to allow the objects on the pinched moving web to pass through the rollers. The groove (or grooves) is (are) shaped and sized to provide clearance for the attached objects to pass through as the film is pulled through the nip of the rollers.
However, the variety of manufacturing methods and bag sizes limits the versatility of hard rollers with peripheral grooves. In each application, the grooves on the rollers must be aligned with the position of the slider on the moving web. For example, slider-zipper assemblies can be attached to a web of bag making film either transversely or aligned with the machine direction. Also, the slider-zipper assembly can be placed anywhere on the web, so that the slider could be near one edge or the other or anywhere between. To account for these differences, the grooved pinch rollers need to be specific to the particular style or size of slider bag being made. This requires a large inventory of grooved rollers, which increases capital costs. Also the need to install different rollers on an automated production line increases downtime, resulting in lost productivity.
There is a need for a roller design that would allow a slider or other object being carried on a web of film to pass through the same set of rollers regardless of the lateral position of the slider (or other object) on the web.